Cryptology ePrint Archive: Report 2005/326

Abstract: Since the introduction of Identity-based (ID-based) cryptography
by Shamir in 1984, numerous ID-based signature schemes have been
proposed. In 2001, Rivest et al. introduced ring signature that
provides irrevocable signer anonymity and spontaneous group
formation. In recent years, ID-based ring signature schemes have
been proposed and all of them are based on bilinear pairings. In
this paper, we propose the first ID-based threshold ring signature
scheme that is not based on bilinear pairings. We also propose the
first ID-based threshold `linkable' ring signature scheme. We
emphasize that the anonymity of the actual signers is maintained
even against the private key generator (PKG) of the ID-based
system. Finally we show how to add identity escrow to the two
schemes. Due to the different levels of signer anonymity they
support, the schemes proposed in this paper actually form a suite
of ID-based threshold ring signature schemes which is applicable
to many real-world applications with varied anonymity
requirements.